The Mexican Navy said on Sunday it arrested the alleged regional head of the feared "Zetas" drug gang in connection with this month's murder of a U.S. customs agent by a drug gang.

The Navy said in a statement that Marines arrested Sergio
"El Toto" Mora, the alleged head of the Zetas in San Luis Potosi, in
a Sunday morning raid in the northern city of Saltillo.

Mora was to be transported to Mexico City and
handed over to the federal prosecutors' office for interrogation.

The statement did not provide further details of Mora's
suspected role in the killing.

A news conference where Mora was to be presented to
journalists in Mexico City was canceled shortly before it was supposed to begin
Sunday evening.

U.S. Immigration and Customs Enforcement (ICE) agent
Jaime Zapata died and his partner was wounded when they were ambushed in broad
daylight on a major highway outside of the city of San Luis Potosi earlier this
month by alleged drug gang members.

It was one of the worst attacks on U.S. law enforcement
personnel in Mexico in more than a decade.

Mexico's federal prosecutors' office believes the attack
was due to a mistaken identity, but it has come under heavy diplomatic pressure
from Washington to capture Zapata's killers.

Security forces have already arrested six men, four women
and a minor in connection with the attack, all of whom are allegedly linked to
the Zetas.

Nine of those arrested were ordered held in prison for 40
days on Sunday by a Mexican judge to allow prosecutors more time to collect
evidence against the suspects before they were charged.

The Zetas, formed by renegade Mexican special forces
soldiers who deserted to become the armed wing of the Gulf Cartel, have grown
in power. They turned on their former masters last year to battle for control
of lucrative drug smuggling routes in northern Mexico.

Escalating drug violence in Mexico, a top U.S. trade
partner, has caused alarm in Washington, which is providing $1.3 billion in
funding and training to help battle the local cartels.

Mexican President Felipe Calderon has made crushing the
cartels a top priority of his government and has sought to enhance cooperation
with U.S. authorities in his fight.

More than 34,000 deaths are blamed on drug violence since
Calderon took office in late 2006 and launched his army led campaign against
the gangs.

**Reporting by Robert Campbell; Editing
by Cynthia Osterman and Paul Simao